For many applications, it is important to keep rapid changes in the load current which is provided by a regulated power supply from being reflected back to the input current. For example, such an application is when a three phase source is used to power single phase equipment. In such an arrangement, the output of the three phase source may be rectified, and then converted to single phase A.C. It is important in such an application to approximately equalize the phase currents at the input, so that a fuse or circuit breaker is not opened on one of the input lines when excessive current flows in it.
In order to prevent rapid changes in load current from being reflected to the input in a buck switching type regulator, the feedback loop may be arranged to be relatively slow. This arrangement will have the effect of spreading any reflection of load current changes into the input over several A.C. cycles. Thus, in the case where a three phase input is used, changes in the load current will be averaged over the three phases, rather than having a pronounced effect on any one phase.
However, when a relatively slow feedback loop is used, the voltage regulation at the load suffers to a certain extent.
While such a feedback loop provides adequate regulation under most operating conditions, if the load voltage should rise rapidly, the feedback loop may not follow fast enough to prevent damage to a circuit component.
It is to the solution of this problem which the present invention is directed.